1. Field of the Invention
The present invention relates to a microcomputer system, a microcomputer, a power supply control method, and a power supply control program product, and particularly to a microcomputer system including a backup power supply, a microcomputer used by the microcomputer system, a power supply control method for the microcomputer, and a power supply control program product used for the microcomputer.
2. Description of Related Art
In recent years, the consciousness of the low power consumption of computer systems is increasing globally. Therefore, lower power consumption of individual computer apparatuses increases the need to tackle to reduce the power consumption of the entire operating system including the computer apparatuses. Further, it is desired to realize lower power consumption of the computer system, and at the same time, to keep the power supply in case of power failure.
Japanese Unexamined Patent Application Publication No. 7-271754 discloses a system to switch the power supply of a microcomputer without evacuating data in a memory to an external memory or the like at the time of blackout, for the purpose of holding data in the state of low power consumption. Specifically, the microcomputer includes a power supply voltage detection circuit to detect a voltage drop of the main power supply. If the power supply voltage detection circuit detects a voltage drop of the main power supply, the microcomputer switches the power supply from main power supply to backup power supply. Further, the microcomputer switches the whole microcomputer to the standby mode with low power consumption. Accordingly, the microcomputer has realized to hold data with low power consumption even if the main power supply is in an abnormal condition.